Impacts of Large-Scale Groundwater Exploitation Based on Long-Term Evolution of Hydraulic Heads in Dhaka City, Bangladesh

Shahina Khatun,Mazeda Islam,Kristine Walraevens,Md Mizanur Rahman Sarker,Marc Van Camp,Delwar Hossain

doi:10.3390/w13101357

Shahina Khatun, Mazeda Islam + Show 4 more

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https://doi.org/10.3390/w13101357

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Abstract

Dhaka city has emerged as the fastest-growing megacity, having more than 20 million inhabitants, with a growth rate of 3.62%. Unplanned and rapid urbanization, coupled with exponential population growth, has significantly altered the groundwater dynamics in Dhaka city. This study concentrates on the evolution of long-term piezometric heads of the Upper Dupi Tila aquifer (UDA) and the Middle Dupi Tila aquifer (MDA) based on long-term hydrographs, piezometric maps and synthetic graphical overviews of piezometric trends. Due to over-exploitation, the piezometric level (PL) has declined deeper than −85 and −65 m PWD (Public Works Department reference datum) in UDA and MDA, respectively. The highest rate of decline was observed in the south-central to southeastern parts of the city both in UDA (4.0 m/year) and MDA (5.74 m/year). The results clearly show that the rates of decline in PL vary from 2.25 to 5.74 m/year in both aquifers of the city, and urban expansion has greatly affected the shape and extent of the depression cone over the past four decades. The magnitudes of the depression cones in both aquifers seem to pose a considerable threat to groundwater resources, indicating that the current exploitation is not sustainable at all.

Highlights

Groundwater overexploitation due to urban expansion and population growth is a critical issue in Dhaka city [1], as it is in many other developing or developed cities in the world such as in Beijing [2,3], Central India [4], the Indus Basin [5], Northwest India [6], Northern Chile [7], California’s Central Valley in the U.S [8], the U.S High Plains [9], the Middle East [10], the Hai River plain in China [11] and Belgium [12], among others
Water table data and piezometric level (PL) data were collected from Bangladesh Water Development Board (BWDB) and Dhaka Water Supply and Sewerage Authority (DWASA) in order to prepare long-term hydrographs and piezometric maps of Upper Dupi Tila aquifer (UDA) and Middle Dupi Tila aquifer (MDA)
The analysis of long-term hydrographs and piezometric maps reveals that the pattern and magnitude of the PL decline from the 1980s onward are directly proportional to the population growth associated with the city’s expansion (Figure 2) and number of deep tube wells (DTWs) installed (Figure 6) in particular parts of the city in a certain period

Summary

Introduction

Groundwater overexploitation due to urban expansion and population growth is a critical issue in Dhaka city [1], as it is in many other developing or developed cities in the world such as in Beijing [2,3], Central India [4], the Indus Basin [5], Northwest India [6], Northern Chile [7], California’s Central Valley in the U.S [8], the U.S High Plains [9], the Middle East [10], the Hai River plain in China [11] and Belgium [12], among others. The capital of Bangladesh, is densely populated and is the largest city in the country. It is the world’s 6th most populated city [25]. It started to expand exponentially after the independence of Bangladesh in 1971. This exponential population growth accelerated groundwater abstraction in order to meet the water demand. In 2018, 78% of the supply water came from underground sources and 22% from treating surface water [26]

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